reaction products of acetic anhydride and adipic acid

Endpoint summary

Description of key information

Oral:
The oral NOAEL (rat) 210 mg/kg bw/day (acetic acid; subchronic)
The oral NOAEL (rat) 290 mg/kg bw/day (acetic acid; subchronic)
The oral NOAEL (rat) 750 mg/kg bw/day (adipic acid; chronic )
Inhalation:
The inhalation NOAEC (rat) 1 ppm (4.2 mg/m3) (acetic anhydride; subchronic)
Dermal:
No relevant studies available

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

210 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Repeated dose toxicity: inhalation - systemic effects

Link to relevant study records

Reference

Endpoint:

short-term repeated dose toxicity: inhalation

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Near guideline study. Conducted for read-across substance, minor restrictions in design and/or reporting but otherwise adequate for assessment. Read-across justification: The available toxicological data for the target and source substances is outlined in the data matrix (Annex I). The toxicological properties of the target substance are related mainly to acetic acid/acetate since the anhydride components of the substance are hydrolytically unstable. When the target substance comes in contact with water or moisture a complete hydrolysis will take place to form no other hydrolysis products than acetic acid/acetate and adipic acid. Thus, the use of data from acetic acid and adipic acid is justified to evaluate toxicological properties of the target substance. Furthermore, data from acetic anhydride is used in the assessment. Experimental data obtained with the source substances indicate that the substances has low oral (LD50 > 1780 – 3310 mg/kg bw) and inhalation (LC50 1680 - 7700 mg/m3) acute toxicity. Furthermore, the acetic acid and acetic anhydride are irritating to skin at concentration < 25% and corrosive to skin at ≥ 25%. Acetic anhydride and acetic acid are not tested for sensitisation due corrosive properties; adipic acid did not show any evidence of sensitising in an animal study. The source substances did not show positive response in genetic toxicity studies available. Repeated toxicity studies via oral route conducted for acetic acid showed NOAEL values ≥ 210 mg kg bw/day and via inhalation route for acetic anhydride 4.2 mg/m3.. Reproduction toxicity studies conducted for acetic acid did not show any adverse effects on reproduction at the highest concentration tested (1600 mg/kg bw/day).

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 412 (Subacute Inhalation Toxicity: 28-Day Study)

Deviations:

yes

Remarks:

No clinical pathology, limited pathology (males only)

Principles of method if other than guideline:

Preliminary range findings study in 5 male and 5 time-mated females per group, exposed to vapours of acetic anhydride for 6h/day for 5 days/week for 2 weeks (males) or from days 6-15 post coitum (females).

GLP compliance:

not specified

Species:

rat

Strain:

other: Crl:CD BR

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River (UK) Ltd, Manston Road, Margate, Kent
- Age at study initiation: Males - approximately 8 weeks old. Females - 9-11 weeks old.
- Housing: 5 / cage in suspended cages with stainless steel mesh floors. The cages of each group were housed on a rack in a separate ventilated chamber to avoid cross contamination following exposures.
- Diet (e.g. ad libitum): SDS Rat and Mouse No. 1 SQC modified maintenance diet. Available in home cages.
- Water (e.g. ad libitum): Tap water available from polypropylene bottles ad libitum in home cages.
- Acclimation period: Males - 12 days, females - 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 18-24°C
- Humidity (%): 40-70%
- Air changes (per hr):
- Photoperiod (hrs dark / hrs light): 12 h light (08.00-20.00) and 12 h dark/24 h.

IN-LIFE DATES: From: 5 January 1994 To: 1 February 1994.

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

other: unchanged (no vehicle)

Remarks on MMAD:

MMAD / GSD: Not applicable

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Stainless steel and glass 0.75m3 whole body chambers
- Method of holding animals in test chamber: singly housed in compartmented stainless steel mesh cages.
- Source and rate of air: Compressed, filtered air, air flow rate not reported.
- Method of conditioning air: Chamber air was pre-warmed by passage through a copper coil immersed in a water bath at 60°C.
- Temperature, humidity, pressure in air chamber: 22.5 - 23.2°C , 23-33% humidity (study mean data), internal pressure of 10mm H2O below ambient.
- Air flow rate: approximately 150L/min.
- Air change rate: Not reported
- Treatment of exhaust air: Drawn through an activated charcoal scrubbing system by an extract fan before being vented to atmosphere.

TEST ATMOSPHERE
- Brief description of analytical method used: Gas chromatography.
- Samples taken from breathing zone: yes

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Acetic anhydride concentration was determined 6 times during each exposure (approximately hourly intervals), using gas chromatography. Samples were also analysed for acetic acid.
The absence of test substance aerosol was confirmed on one occasion during the study using a Royco Particle Monitor.

Duration of treatment / exposure:

5 days/week for 2 weeks (males)
Days 6-15 post coitum (females)

Frequency of treatment:

6 h/day

Remarks:

Doses / Concentrations:
0, 24, 104 ppm (females)
Basis:
analytical conc.

Remarks:

Doses / Concentrations:
0, 24, 103, 407 ppm (males)
Basis:
analytical conc.

Remarks:

Doses / Concentrations:
0, 104, 418 and 1670 mg/m3
Basis:
other: target concentrations

Remarks:

Doses / Concentrations:
0, 25, 100, 400 ppm
Basis:
other: target concentrations

No. of animals per sex per dose:

5

Control animals:

yes, sham-exposed

Details on study design:

Males were exposed to the high dose concentration on one occasion only, due to toxicity and females were not exposed to this concentration (Table 1)

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: During exposure

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Twice daily

BODY WEIGHT: Yes
- Time schedule for examinations: Males - week -1, day 1 (pre-exposure) and then daily thereafter. Females - day 1 of pregnancy and then on days 2, 3, 6, 8, 10, 12, 14, 16, 18 & 20 post coitum.

FOOD CONSUMPTION:
- Food consumption determined and mean diet consumption calculated as g food/rat/day: Yes

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No

WATER CONSUMPTION: Yes
- Time schedule for examinations: Daily, from week -1 in males and from day 1 of pregnancy in females.

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: No

CLINICAL CHEMISTRY: No

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No

OTHER:

Sacrifice and pathology:

Following 2 weeks of exposure, surviving male rats were anaesthetised by IP injection of pentobarbitone sodium and killed by exsanguination.
On day 20 of pregnancy (day 13 for Groups 3 & 4), female rats were killed by CO2 asphyxia, dissected and examined for congenital abnormalities and macroscopic pathological changes in maternal organs.

GROSS PATHOLOGY: Males.- detailed macroscopic examination. Adrenal glands, kidneys, liver, lungs and testes (with epidiymides) were weighed and a range of organs were preserved in fixative.
HISTOPATHOLOGY: Yes - Gross abnormalities, larynx, lung, nasal passages, tongue and trachea from male rats.

Other examinations:

Litter data and foetal examination: for groups 1 and 2 (killed on day 20 of pregnancy),

Statistics:

Not performed due to small group sizes.

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

effects observed, treatment-related

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

no effects observed

Details on results:

CLINICAL SIGNS AND MORTALITY
400 ppm - During exposure all males showed prone posture, half-closed eyes, lachrymation and exaggerated breathing. After exposure all showed noisy respiration. On day 2, pre-exposure, 2 males were found dead. Of the 3 survivors, all had gasping respiration and 2 were lethargic. These 3 animals were sacrificed due to their poor condition. No females were exposed to 400 ppm.
100 ppm - During exposure, males and females showed half-closed eyes, licking the inside of the mouth, lachrymation, gasping and/or exaggerated respiration and occasional twitching of the head. Post exposure, all animals showed noisy respiration and occasional sneezing and gasping respiration. Females also showed arching of the back and head twitching. Due to the severity of these clinical signs and general poor condition, males were terminated after 6 exposures and females after 7 exposures.
25 ppm - There were no mortalities. During exposure, males and females showed half-closed eyes, licking the inside of the mouth and occasional twitching of the head, particularly on the last 3-4 days of exposure. Post exposure, all animals had noisy respiration and, in females, this continued for 4 days after the last exposure.
BODY WEIGHT AND WEIGHT GAIN
400 ppm - All animals showed weight loss of approximately 50 g following the first exposure.
100 ppm - Marked bodyweight loss was seen in all animals following each exposure.
25 ppm - males showed no effects on body weight during the first week of exposure, however during the second week, body weight loss followed by reduced gain was seen. Following the last exposure, body weight gain improved. In females, there was no effect on bodyweight following the first two exposures (day 8 of pregnancy) but thereafter, body weight gain was lower than controls until the end of exposures. On cessation of exposures, there was a marked recovery in body weight.
FOOD CONSUMPTION
400 ppm - The group mean cage value for food consumption was almost zero after the first exposure.
100 ppm - Marked reductions in food consumption were seen in both sexes following each exposure.
25 ppm - Group mean food consumption was slightly lower than controls throughout the exposure periods and was comparable to controls following cessation of exposures.
WATER CONSUMPTION
400 ppm - The group mean cage value for water consumption was almost zero after the first exposure.
100 ppm - Marked reductions in water consumption were seen in both sexes following each exposure.
25 ppm - Group mean water consumption was slightly lower than controls throughout the exposure periods and was comparable to controls following cessation of exposures.
ORGAN WEIGHTS
25 ppm - lung weight was higher and liver and kidney weights were lower in males compared to controls.
Organs were not weighed in females.
GROSS PATHOLOGY
400 ppm - All males showed gaseous distension in the gastrointestinal tract, particularly in the stomach. In addition most animals showed brown perinasal staining.
100 ppm - All males and two females had gaseous distension at one or more levels of the gastrointestinal tract. All males had enlarged cervical and/or tracheobronchial lymph nodes and most showed minimal adipose tissue.
25 ppm - All males had enlarged cervical and/or tracheobronchial lymph nodes and two had congestion in the anterior lobe of the right lung.
There were no treatment related macroscopic abnormalities in females.
HISTOPATHOLOGY: NON-NEOPLASTIC
400ppm - severe degenerative changes were seen in nasal passages, larynx, trachea and tracheal bifurcation and lungs, comprising rhinitis, epithelial ulceration/ degeneration with associated inflammatory exudate and/or epithelial hyperplasia/squamous metaplasia.
100 ppm - severe/slightly less severe degenerative changes were seen in nasal passages, larynx, trachea and tracheal bifurcation and lungs, comprising rhinitis, epithelial ulceration/ degeneration with associated inflammatory exudate and/or epithelial hyperplasia/squamous metaplasia. There was evidence of regenerative hyperplasia and hypertrophy in the lungs. Lymphoid proliferation was seen in macroscopically abnormal lymph nodes.
25 ppm - changes were less severe and comprised rhinitis and hyperplasia in the nasal passages, epithelial hyperplasia and squamous metaplasia in the larynx, slight epithelial hyperplasia in the trachea, epithelial hypertrophy with goblet cells in the lungs and lymphoid proliferation in macroscopically abnormal lymph nodes.
OTHER FINDINGS
Reproductive effects:
100 ppm - 4/5 females were pregnant and 2 showed total resorption of their litters. The other 2 were supporting live litters of comparable size to the concurrent control group (Group 4 unexposed females also killed on day 13 post coitum). Examination of the foetuses for visible abnormalities was not fully possible given the age at sacrifice.
25 ppm - All females had a live litter at termination (day 20 post coitum). The incidence and pattern of embryofoetal loss, litter size, litter weight and foetal weight were similar to controls and there were no gross foetal abnormalities.

Dose descriptor:

LOAEC

Effect level:

104 mg/m³ air

Sex:

male/female

Basis for effect level:

other: (25 ppm) clinical signs; body weight; food consumption; water consumption; gross pathology; histopathology;

Critical effects observed:

not specified

Executive summary:

In consideration of the marked acute toxic treatment-related effects (clinical, macroscopic and microscopic) seen among males exposed at 400 ppm, and the less marked but clear toxic effects seen in both sexes exposed at 100ppm, neither of these levels would be suitable for further investigation in studies with a longer period of treatment.

At an exposure level of 25 ppm, there was clear evidence of toxicity in both sexes, and although tolerable for 10 days of exposure, changes were similar to, but less severe than, at higher exposure levels. Thus, in a longer period of exposure, this exposure level may prove too high and, as such, should only serve as an upper level from which dosages can be selected.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEC

4.2 mg/m³

Study duration:

subchronic

Species:

rat

Repeated dose toxicity: inhalation - local effects

Link to relevant study records

Reference

Endpoint:

short-term repeated dose toxicity: inhalation

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Near guideline study. Conducted for read-across substance, minor restrictions in design and/or reporting but otherwise adequate for assessment. Read-across justification: The available toxicological data for the target and source substances is outlined in the data matrix (Annex I). The toxicological properties of the target substance are related mainly to acetic acid/acetate since the anhydride components of the substance are hydrolytically unstable. When the target substance comes in contact with water or moisture a complete hydrolysis will take place to form no other hydrolysis products than acetic acid/acetate and adipic acid. Thus, the use of data from acetic acid and adipic acid is justified to evaluate toxicological properties of the target substance. Furthermore, data from acetic anhydride is used in the assessment. Experimental data obtained with the source substances indicate that the substances has low oral (LD50 > 1780 – 3310 mg/kg bw) and inhalation (LC50 1680 - 7700 mg/m3) acute toxicity. Furthermore, the acetic acid and acetic anhydride are irritating to skin at concentration < 25% and corrosive to skin at ≥ 25%. Acetic anhydride and acetic acid are not tested for sensitisation due corrosive properties; adipic acid did not show any evidence of sensitising in an animal study. The source substances did not show positive response in genetic toxicity studies available. Repeated toxicity studies via oral route conducted for acetic acid showed NOAEL values ≥ 210 mg kg bw/day and via inhalation route for acetic anhydride 4.2 mg/m3.. Reproduction toxicity studies conducted for acetic acid did not show any adverse effects on reproduction at the highest concentration tested (1600 mg/kg bw/day).

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 412 (Subacute Inhalation Toxicity: 28-Day Study)

Deviations:

yes

Remarks:

No clinical pathology, limited pathology (males only)

Principles of method if other than guideline:

Preliminary range findings study in 5 male and 5 time-mated females per group, exposed to vapours of acetic anhydride for 6h/day for 5 days/week for 2 weeks (males) or from days 6-15 post coitum (females).

GLP compliance:

not specified

Species:

rat

Strain:

other: Crl:CD BR

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River (UK) Ltd, Manston Road, Margate, Kent
- Age at study initiation: Males - approximately 8 weeks old. Females - 9-11 weeks old.
- Housing: 5 / cage in suspended cages with stainless steel mesh floors. The cages of each group were housed on a rack in a separate ventilated chamber to avoid cross contamination following exposures.
- Diet (e.g. ad libitum): SDS Rat and Mouse No. 1 SQC modified maintenance diet. Available in home cages.
- Water (e.g. ad libitum): Tap water available from polypropylene bottles ad libitum in home cages.
- Acclimation period: Males - 12 days, females - 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 18-24°C
- Humidity (%): 40-70%
- Air changes (per hr):
- Photoperiod (hrs dark / hrs light): 12 h light (08.00-20.00) and 12 h dark/24 h.

IN-LIFE DATES: From: 5 January 1994 To: 1 February 1994.

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

other: unchanged (no vehicle)

Remarks on MMAD:

MMAD / GSD: Not applicable

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Stainless steel and glass 0.75m3 whole body chambers
- Method of holding animals in test chamber: singly housed in compartmented stainless steel mesh cages.
- Source and rate of air: Compressed, filtered air, air flow rate not reported.
- Method of conditioning air: Chamber air was pre-warmed by passage through a copper coil immersed in a water bath at 60°C.
- Temperature, humidity, pressure in air chamber: 22.5 - 23.2°C , 23-33% humidity (study mean data), internal pressure of 10mm H2O below ambient.
- Air flow rate: approximately 150L/min.
- Air change rate: Not reported
- Treatment of exhaust air: Drawn through an activated charcoal scrubbing system by an extract fan before being vented to atmosphere.

TEST ATMOSPHERE
- Brief description of analytical method used: Gas chromatography.
- Samples taken from breathing zone: yes

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Acetic anhydride concentration was determined 6 times during each exposure (approximately hourly intervals), using gas chromatography. Samples were also analysed for acetic acid.
The absence of test substance aerosol was confirmed on one occasion during the study using a Royco Particle Monitor.

Duration of treatment / exposure:

5 days/week for 2 weeks (males)
Days 6-15 post coitum (females)

Frequency of treatment:

6 h/day

Remarks:

Doses / Concentrations:
0, 24, 104 ppm (females)
Basis:
analytical conc.

Remarks:

Doses / Concentrations:
0, 24, 103, 407 ppm (males)
Basis:
analytical conc.

Remarks:

Doses / Concentrations:
0, 104, 418 and 1670 mg/m3
Basis:
other: target concentrations

Remarks:

Doses / Concentrations:
0, 25, 100, 400 ppm
Basis:
other: target concentrations

No. of animals per sex per dose:

5

Control animals:

yes, sham-exposed

Details on study design:

Males were exposed to the high dose concentration on one occasion only, due to toxicity and females were not exposed to this concentration (Table 1)

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: During exposure

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Twice daily

BODY WEIGHT: Yes
- Time schedule for examinations: Males - week -1, day 1 (pre-exposure) and then daily thereafter. Females - day 1 of pregnancy and then on days 2, 3, 6, 8, 10, 12, 14, 16, 18 & 20 post coitum.

FOOD CONSUMPTION:
- Food consumption determined and mean diet consumption calculated as g food/rat/day: Yes

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No

WATER CONSUMPTION: Yes
- Time schedule for examinations: Daily, from week -1 in males and from day 1 of pregnancy in females.

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: No

CLINICAL CHEMISTRY: No

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No

OTHER:

Sacrifice and pathology:

Following 2 weeks of exposure, surviving male rats were anaesthetised by IP injection of pentobarbitone sodium and killed by exsanguination.
On day 20 of pregnancy (day 13 for Groups 3 & 4), female rats were killed by CO2 asphyxia, dissected and examined for congenital abnormalities and macroscopic pathological changes in maternal organs.

GROSS PATHOLOGY: Males.- detailed macroscopic examination. Adrenal glands, kidneys, liver, lungs and testes (with epidiymides) were weighed and a range of organs were preserved in fixative.
HISTOPATHOLOGY: Yes - Gross abnormalities, larynx, lung, nasal passages, tongue and trachea from male rats.

Other examinations:

Litter data and foetal examination: for groups 1 and 2 (killed on day 20 of pregnancy),

Statistics:

Not performed due to small group sizes.

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

effects observed, treatment-related

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

no effects observed

Details on results:

CLINICAL SIGNS AND MORTALITY
400 ppm - During exposure all males showed prone posture, half-closed eyes, lachrymation and exaggerated breathing. After exposure all showed noisy respiration. On day 2, pre-exposure, 2 males were found dead. Of the 3 survivors, all had gasping respiration and 2 were lethargic. These 3 animals were sacrificed due to their poor condition. No females were exposed to 400 ppm.
100 ppm - During exposure, males and females showed half-closed eyes, licking the inside of the mouth, lachrymation, gasping and/or exaggerated respiration and occasional twitching of the head. Post exposure, all animals showed noisy respiration and occasional sneezing and gasping respiration. Females also showed arching of the back and head twitching. Due to the severity of these clinical signs and general poor condition, males were terminated after 6 exposures and females after 7 exposures.
25 ppm - There were no mortalities. During exposure, males and females showed half-closed eyes, licking the inside of the mouth and occasional twitching of the head, particularly on the last 3-4 days of exposure. Post exposure, all animals had noisy respiration and, in females, this continued for 4 days after the last exposure.
BODY WEIGHT AND WEIGHT GAIN
400 ppm - All animals showed weight loss of approximately 50 g following the first exposure.
100 ppm - Marked bodyweight loss was seen in all animals following each exposure.
25 ppm - males showed no effects on body weight during the first week of exposure, however during the second week, body weight loss followed by reduced gain was seen. Following the last exposure, body weight gain improved. In females, there was no effect on bodyweight following the first two exposures (day 8 of pregnancy) but thereafter, body weight gain was lower than controls until the end of exposures. On cessation of exposures, there was a marked recovery in body weight.
FOOD CONSUMPTION
400 ppm - The group mean cage value for food consumption was almost zero after the first exposure.
100 ppm - Marked reductions in food consumption were seen in both sexes following each exposure.
25 ppm - Group mean food consumption was slightly lower than controls throughout the exposure periods and was comparable to controls following cessation of exposures.
WATER CONSUMPTION
400 ppm - The group mean cage value for water consumption was almost zero after the first exposure.
100 ppm - Marked reductions in water consumption were seen in both sexes following each exposure.
25 ppm - Group mean water consumption was slightly lower than controls throughout the exposure periods and was comparable to controls following cessation of exposures.
ORGAN WEIGHTS
25 ppm - lung weight was higher and liver and kidney weights were lower in males compared to controls.
Organs were not weighed in females.
GROSS PATHOLOGY
400 ppm - All males showed gaseous distension in the gastrointestinal tract, particularly in the stomach. In addition most animals showed brown perinasal staining.
100 ppm - All males and two females had gaseous distension at one or more levels of the gastrointestinal tract. All males had enlarged cervical and/or tracheobronchial lymph nodes and most showed minimal adipose tissue.
25 ppm - All males had enlarged cervical and/or tracheobronchial lymph nodes and two had congestion in the anterior lobe of the right lung.
There were no treatment related macroscopic abnormalities in females.
HISTOPATHOLOGY: NON-NEOPLASTIC
400ppm - severe degenerative changes were seen in nasal passages, larynx, trachea and tracheal bifurcation and lungs, comprising rhinitis, epithelial ulceration/ degeneration with associated inflammatory exudate and/or epithelial hyperplasia/squamous metaplasia.
100 ppm - severe/slightly less severe degenerative changes were seen in nasal passages, larynx, trachea and tracheal bifurcation and lungs, comprising rhinitis, epithelial ulceration/ degeneration with associated inflammatory exudate and/or epithelial hyperplasia/squamous metaplasia. There was evidence of regenerative hyperplasia and hypertrophy in the lungs. Lymphoid proliferation was seen in macroscopically abnormal lymph nodes.
25 ppm - changes were less severe and comprised rhinitis and hyperplasia in the nasal passages, epithelial hyperplasia and squamous metaplasia in the larynx, slight epithelial hyperplasia in the trachea, epithelial hypertrophy with goblet cells in the lungs and lymphoid proliferation in macroscopically abnormal lymph nodes.
OTHER FINDINGS
Reproductive effects:
100 ppm - 4/5 females were pregnant and 2 showed total resorption of their litters. The other 2 were supporting live litters of comparable size to the concurrent control group (Group 4 unexposed females also killed on day 13 post coitum). Examination of the foetuses for visible abnormalities was not fully possible given the age at sacrifice.
25 ppm - All females had a live litter at termination (day 20 post coitum). The incidence and pattern of embryofoetal loss, litter size, litter weight and foetal weight were similar to controls and there were no gross foetal abnormalities.

Dose descriptor:

LOAEC

Effect level:

104 mg/m³ air

Sex:

male/female

Basis for effect level:

other: (25 ppm) clinical signs; body weight; food consumption; water consumption; gross pathology; histopathology;

Critical effects observed:

not specified

Executive summary:

In consideration of the marked acute toxic treatment-related effects (clinical, macroscopic and microscopic) seen among males exposed at 400 ppm, and the less marked but clear toxic effects seen in both sexes exposed at 100ppm, neither of these levels would be suitable for further investigation in studies with a longer period of treatment.

At an exposure level of 25 ppm, there was clear evidence of toxicity in both sexes, and although tolerable for 10 days of exposure, changes were similar to, but less severe than, at higher exposure levels. Thus, in a longer period of exposure, this exposure level may prove too high and, as such, should only serve as an upper level from which dosages can be selected.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEC

4.2 mg/m³

Study duration:

subchronic

Species:

rat

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

No specific studies have been conducted for the target substance.The target substance is composed of acetic anhydride (typical conc. ca. 7 wt. %), adipic acid, di-anhydride with bis (acetic acid) (typical conc. ca. 57 wt. %) and acetic acid (typical conc. ca. 33 wt. %).The most hazardous component of this substance is acetic anhydride which has well-known corrosive and irritating effects on the eyes, skin and respiratory tract.

The weight of evidence approach is used to evaluate the hazardous properties of the target substance after repeated exposure. Thus, the data from acetic anhydride and from the final hydrolysis products of the target substance (acetic acid/acetate and adipic acid), are used in the assessment.

Repeated oral toxicity

Acetic acid toxicity is assessed via toxicity observed after administration of methyltriacetoxysilane in animals. Methyltriacetoxysilane undergoes rapid hydrolysis in moist/aqueous environments (t1/2 < 12 seconds) to acetic acid and the corresponding trisilanols. Thus observed toxicity is likely due primarily to acetic acid. In a 7-day oral range-finding study (gavage) rats were treated with 0, 100, 500 and 1000 mg/kg bw/day. Animals from the 100 mg/kg/day dose groups survived to day 7. Animals from the 500 and 1000 mg/kg/day dose groups were sacrificed after the third dose as a consequence of two deaths (one from each group), marked body weight loss, and severity of lesions (ulceration and erosion of stomach and esophagus) observed in necropsied animals. The stomach lesions observed resembled irritation from acetic acid production. This 7-day range-finder study indicated that a maximum dose level of less than 100 mg/kg bw/day would be required for a longer duration repeated dose study in order to avoid death or obvious suffering due to the corrosivity of the hydrolysis product, acetic acid. Further studies which used lower doses of acetic acid and its salts showed NOAEL values ranging from 210 mg/kg bw/day (2-4 month acetic acid drinking water study; systemic toxicity) to 3600 mg/kg bw/day (acetic acid, sodium salt, 4 week dietary study; no effects reported). (HSDB, 2016).

To clarify the possibility of a preventive effect of dietary vinegar on blood pressure, long-term administration of vinegar or the acetic acid to Spontaneously Hypertensive Rats was examined (Kondo, S. et al., 2001). As a result, it was observed that acetic acid itself, the main component of vinegar, significantly reduced both blood pressure (p<0.05) and renin activity (p<0.01), compared to controls given no acetic acid or vinegar, as well as vinegar. There were no significant differences in angiotensin I-converting enzyme activity in various organs. As for the mechanism of this function, it was suggested that this reduction in blood pressure may because by the significant reduction in renin activity and the subsequent decrease in angiotensin II. From this study, it was also suggested that the antihypertensive effect of vinegar is mainly due to the acetic acid in it. Based on this study the NOAEL of 290 mg/kg bw/d was established.

There are available few studies which can be used to assess the toxicity of adipic acid after repeated exposure.However, the studies do not comply with the current guidelines and are very limited in their reliability. After repeated administration of NOAEL values range from 750 mg/kg bw/day (adipic acid, chronic dietary study, rat) to 3333 mg mg/kg bw/day (sodium adipate, chronic dietary study, rat) OECD; SIDS (2003).

Repeated inhalation toxicity

Acetic anhydride is highly irritating and readily hydrolyzes to acetic acid. Therefore, local toxicity at site of contact is observed, but not systemic toxicity. This is demonstrated by the following inhalation studies.

In a two-week inhalation study (OECD; SIDS, 1997), respiratory tract irritation was reported in rats exposed for 6 hr/day, 5 days per week (or less) to 25, 100 or 400 ppm acetic anhydride vapor. Mortality (40%) was observed in the 400 ppm group after the first 6-hr. exposure period and additional exposures were not conducted in this group. As respiratory tract irritation was observed at all levels tested, no NOAEL was established.

In a13-week inhalation study (OECD; SIDS, 1997), rats were exposed for 6 h/day, 5 days/week to 1, 5 or 20 ppm acetic anhydride vapor. Each group contained 15 male and 15 female animals. Clinical observations of eye and respiratory tract irritation and reduced body weights were observed primarily at 20 ppm. Microscopic examination of tissues revealed signs of irritation of minimal severity in the respiratory tract (nasal passages; larynx) in most animals at the 5 ppm level. At 20 ppm, all animals showed minimal to moderate respiratory tract irritation (nasal passages; larynx; trachea; lungs). Systemic effects were not observed at 5 or 20 ppm. No effects were detected at 1 ppm. In animals exposed to the same levels of acetic anhydride for 13 weeks and then allowed a 13-week period without exposure, significant recovery from irritation effects was reported. In summary, the effects were consistent with those typical of substances which act as local/site-of-contact irritants. The NOEL was concluded to be 1 ppm (4.2 mg/m3).

Male and female rats exposed to adipic acid as an aerosol (126 µg/m³, 6 hr daily for 15 days) showed no signs of toxicity. Blood parameters at euthanasia and organ pathology at autopsy were normal. (Bingham, et al 2001)

 

Repeated dermal toxicity

There are no relevant dermal studies available for the target substance or the constituents. Furthermore, dermal route is not considered to be relevant exposure route, as skin contact is not likely during the production and use of the test substance because of adequate RMMs in use (see sections 9&10 of CSR).

Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:
No study was selected as the endpoint conclusion is based on the WoE from several studies

Justification for selection of repeated dose toxicity inhalation - systemic effects endpoint:
A good quality study was conducted for the most hazardous constituent of the target substance according to the OECD guideline and in compliance with GLP.

Justification for selection of repeated dose toxicity inhalation - local effects endpoint:
A good quality study was conducted for the most hazardous constituent of the target substance according to the OECD guideline and in compliance with GLP.

Justification for selection of repeated dose toxicity dermal - systemic effects endpoint:
Dermal route is not considered to be relevant exposure route, as skin contact is not likely during the production and use of the test substance because of adequate RMMs in use.

Justification for selection of repeated dose toxicity dermal - local effects endpoint:
Dermal route is not considered to be relevant exposure route, as skin contact is not likely during the production and use of the test substance because of adequate RMMs in use

Justification for classification or non-classification

Based on the observations made after the repeated exposure of acetic anhydride, acetic acid and adipic acid there is no need to classify the target substance for repeated dose toxicity in accordance with the criteria of CLP Regulation 1272/2008.